Hydrofoil watercraft

ABSTRACT

The watercraft has a fore hydrofoil and an aft carried hydrofoil arranged in the &#39;&#39;&#39;&#39;tandem&#39;&#39;&#39;&#39; manner. The fore hydrofoil includes a central portion and two side portions of which the upper extremities are located above the water line corresponding to the cruising speed of the watercraft. The angles of deadrise, or lateral rise of the side portions of the fore hydrofoil are diminishing in the direction from the diametral central plane of the watercraft toward the sides thereof. This diminishing of the angles of lateral rise starts from the depth of submergence in respect of the cruising speed water line, not smaller than half a chord of the fore hydrofoil measured in place of intersection thereof with the water line corresponding to the cruising speed.

United States Patent Erlykin et al. 1 Sept. 26, 1972 [54] HYDROFOIL WATERCRAFT [52] US. Cl. ..ll4/66.5 H 72 I t z I I I h E I Int- CL"... ..B63b I 1 ,;f"1j y 2,232 58 Field of Search ..1 14/665 H lvanovich Vasin, Jubileiny bulvar, 7, kv. 17; Mikhail Mikhailovich Korot- [561 References Cit! kov, Sormovskoe shosse, 4, kv. 2; N D Vadim Yakovlevich Maximov, ulitsa U [TE STATES PATENTS svetlayarskaya 50 kv Ivan Steinberg .-l H [vanovich Matveev, ulitsa 3,464,377 9/1969 Von Schertel ..l l4/66.5 H

Filed:

stage, 6, kv. 75; Vladimir Alexandrovich Kadyshev, ulitsa C hernyakhorvskago, 8, kv. 6; Valentin Vladimirovich Volkov, prospekt Gagarina, 20, kv. 55; Vladlen Borisovich Firsel, ulitsa Zavodsky Park, 18, kv. 1; Vladimir Dmitrievich Bulatkin, ulitsa Sudostroitelnaya, 4, kv. 1; Igor Evgenievich Malekhanov, ulitsa Dzerzhinskogo, 8, kv. l9; Stanislav Nikolaevich Suldin, ulitsa Kominterna, 123, kv. 2, all of Gorky, U.S.S.R.

May 20, 1971 Appl. No.: 145,180

Foreign Application Priority Data Dec. 9, 1970 Sept. 7, 1970 Primary Examiner-Andrew H. Farrell Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT The watercraft has a fore hydrofoil and an aft carried hydrofoil arranged in the tandem manner.

The fore hydrofoil includes a central portion and two side portions of which the upper extremities are located above the water line corresponding to the cruising speed of the watercraft.

The angles of deadrise, or lateral rise of the side portions of the fore hydrofoil are diminishing in the direction from the diametral central plane of the watercraft toward the sides thereof. This diminishing of the angles of lateral rise starts from the depth of submergence in respect of the cruising speed water line, not smaller than half a chord of the fore hydrofoil measured in place of intersection thereof with the water line corresponding to the cruising speed.

7 Claims, 11 Drawing Figures PATENTEDSEPZS c972 .SHEEI 2 [1F 3 FIG. 3

FIG. 6

HYDROFOIL WATERCRAFT The present invention relates to the art of building watercraft, and, more particularly, it relates to hydrofoil watercraft.

The present invention can be incorporated to the utmost advantage in hydrofoil watercraft with the socalled tandem arrangement of the hydrofoils thereof.

The weight of such watercraft at a cruising speed of its travel is taken up by the dynamic lift forces furnished by the fore and aft carrier hydrofoils mounted downward of the hull of the watercraft, respectively, to the fore and to the aft of the gravity I center thereof. The spacing between the fore and aft carrier hydrofoils is selected so that the aft hydrofoil should always be at the rising incline of the water wave produced on account of the deformation of the free surface of water behind the fore hydrofoil, as the watercraft is travelling at a cruising speed.

There are already known hydrofoil watercraft with .the tandem" arrangement of the hydrofoils, wherein the fore hydrofoil has a central portion merging at the side ends thereof with two side portions.

These side portions of the fore carrier hydrofoil of the known watercraft intersect the surface of water at a cruising speed of the watercraft so that their upper extremities are located above the water line corresponding to the cruising speed. The central portion of this hydrofoil is located at the depth of submergence in respect of said cruising speed water line, which is in excess of a half of the chord measured in place of intersection of the side portions of the fore hydrofoil with the surface of water at said cruising speed.

At present, the fore hydrofoil of such hydrofoi watercraft has the angle of deadrise or lateral rise of the side portions thereof either permanent or gradually increasing in the direction from the diametral central plane of the watercraft toward the sides thereof.

- Among the disadvantages of such a structure of the fore carrier hydrofoil is the fact that the stream of water deformed thereby displays in the area of the rising incline of the water wave considerable nonuniformity of the cross-sectional profile of the trough of the wave, whereby there is non-uniform distribution of the positive incline of'the water stream along the span of the aft hydrofoil. This hinders the effective use of the stream in the tandem system, both at a cruising speed of the watercraft and during transitory periods.

Another disadvantage of hydrofoil watercraft having the fore hydrofoil of the above described structure is the considerable overall width dimensions of the hydrofoil, resulting from the necessity of ensuring sufficient seaworthiness and roll stability of the watercraft, when it travels on the hydrofoils.

For instance, increase of depth of submergence of the central portion of such a fore hydrofoil, due to the increased angle of lateral rise of the side portions thereof and increase of clearance of the hull above the water level requires, in order to ensure sufficient roll stability of the watercraft, the corresponding increase of the arm of the stabilizing forces in respect of the gravity centre of the watercraft, when the latter rolls. This is attained in such watercraft by increased lateral spacing of the side portions of the fore hydrofoil, i.e. by increasing the overall width of the fore hydrofoil.

Besides, the considerable dead rise or lateral rise of the side portions of the fore hydrofoil above the cruising speed water line, which is inherent in the above described known structure of the fore hydrofoil, results in the appearance of considerable lateral drift forces, when the watercraft travels across water with skew roughness, whereby the seaworthiness of such hydrofoil watercraft is adversely affected.

It is an object of the present invention to create a hydrofoil watercraft, which should feature improved hydrodynamic properties attained by the increased efficiency of the interaction of the tandem hydrofoils thereof, both at a cruising speed and during transitory periods of the travel of the craft.

It is another object of the present invention to create a hydrofoil watercraft which should combine improved seaworthiness with reduced overall width dimensions of the fore hydrofoil.

With these and other object in view, the side portions of the fore hydrofoil have, in accordance with the present invention, the angles of deadrise, or lateral rise diminishing in the direction from the diametral central plane of the craft, such diminishing starting from the depth of submergence of said side portions in respect of the cruising speed water line, which is not smaller than half a chord of said fore hydrofoil in place of intersection thereof with the surface of water at said cruising speed, the central portion of said hydrofoil having the angles of lateral rise thereof not exceeding the respective angles of lateral rise of said side portions at the points where they merge with said central portion.

It is advisable that, with the angles of lateral rise of the central portion of the fore hydrofoil being smaller than the respective angles of the dead rise or lateral rise of the side portions at points where they merge with the central portion, the incidence angles of the normal sections of the central portion should be smaller than the incidence angles of the normal sections of the side portions located at the depth of submergence (at a cruising speed) in excess of half a chord of the fore hydrofoil, measured in place of intersection thereof with the surface of water at a cruising speed.

In one embodiment of the present invention there is provided a stabilizer mounted above the fore hydrofoil, this stabilizer being formed as a foil having the span thereof not smaller than the width of the hull of the watercraft at the point where the stabilizer is mounted thereon.

It is advisable that the height of the stabilizer above the fore hydrofoil should not exceed the chord of the upper extremities of the side portions of the fore hydrofoil.

It is further advisable for said stabilizer to be of a split structure and for the spacing between the internal ends of the two portions, facing the diametral central plane of the watercraft, not to exceed the width of the hull of the watercraft at the area where the stabilizer is mounted thereon.

According to another embodiment of the present invention, there is mounted intermediate of the fore and aft carrier hydrofoils, to the aft from the gravity centre of the watercraft, above the cruising speed water line, middle hydrofoil having a relatively small angle of lateral rise and a span not smaller than the width of the hull of the watercraft at the bilge thereof at the point where the middle hydrofoil is mounted thereon.

It is further advisable to have flaps pivotally mounted on the central portion of the fore hydrofoil and on the side end portions of the aft hydrofoil, symmetrically in respect 'of the diametral central plane of the watercraft, these flaps being meant to assist in stabilization of the watercraft when it travels on rough seas.

The structure of a hydrofoil watercraft embodying the present invention increases the efficiency of the interaction of the tandem-arranged hydrofoils and thus improves the hydrodynamic properties of the watercraft both at a cruising speed and during transitory periods of its travel; it furnishes improved seaworthiness, combined with a reduced overall width of the fore hydrofoil.

The present invention will be better understood from the following detailed description of an embodiment thereof, with reference being made to the accompanying drawings, wherein:

FIG. 1 shows schematically the perspective general view of a hydrofoil watercraft embodying the invention;

FIG. 2 shows the hull portion of the watercraft (a side view with the cruising speed waterline indicated);

FIG. 3 illustrates the fore and the aft carrier hydrofoils in an operating position at a cruising speed (an axonometric projection);

FIG. 4 is a view taken along the arrow line A in FIG. 2 at the fore hydrofoil (for convenience, the struts and the stabilizer are not shown);

FIG. 5 is a view taken along arrow line B in FIG. 4;

FIG. 6 is a cross-sectional view taken along line C- C in FIG. 4;

FIG. 7 is a cross-sectional view taken along line D D in FIG. 4;

FIG. 8 is a sectional view taken along line EE in FIG. 2;

FIG. 9 is a sectional view taken along line E-E in FIG. 2 (with an alternative structure of the stabilizer);

FIG. 10 is a sectional view taken along line F-F in FIG. 2;

FIG. 11 is a longitudinally sectional view along the diametral central plane of the watercraft (with indication of the waterlines corresponding to various phases of the travel of the watercraft).

Referring now in particular to the appended drawings, a hydrofoil watercraft comprises body 1 (FIG. 1) on the hull of which there are mounted by means of struts 2 a fore, or bow carrier hydrofoil 3 and an aft, or stem carrier hydrofoil 4. l-Iydrofoils 3 and 4 which are arranged one behind the other in the tandem" fashion, respectively, forwardly and backwardly of gravity centre 5 (FIG. 2) of the watercraft, are adapted to create a hydrodynamic lifting force taking up the weight of the watercraft when the latter travels at a cruising speed.

Fore hydrofoil 3 includes a horizontal central portion sured at the point where side hydrofoil portions 3b intersect the surface of water at a cruising speed of th watercraft.

The aft, or stern hydrofoil 4 is disposed backwardly of fore hydrofoil 3, at such a distance from the latter that aft hydrofoil 4 should be positioned at rising incline 6a of the water wave (FIGS. 2 and 3) formed on account of the deformation of the free surface of water backwardly of fore carrier hydrofoil 3 at a cruising speed of the watercraft.

Each one of two side portions 3b of force hydrofoil 3 has varying angle d), 4: and 5 (FIG. 4) of lateral rise, diminishing in the direction from the diametral, or central plane 7 of the watercraft toward the respective sides of the watercraft, so that the following condition is maintained: (1), This relationship between the angles (b, (1) 4a, of dead rise or lateral rise is true, starting from depth h measured from water line 6, this depth of submergence 11" being not less than one half of the abovementioned chord 0" of fore hydrofoil 3. Angle 4b,, of dead rise or lateral rise of central portion 3a of hydrofoil 3 should not be greater than angle qS, of lateral rise of side portions 3b at points where they merge with central portion 3a; for example, angle 11 may be equal to zero, as is shown in solid lines in FIGS. 3 and 4.

The character of the variation of angles 4:, (b 41 of lateral rise of side portions 3b, starting from the abovespecified depth of submergence h, may be different from that illustrated in the appended drawings; for instance, this variation may be continuous, in cases when side portions 3b are shaped as arcs of a circle.

Whether central portion 30 has the angle of dead rise or lateral rise equalling zero or some angle (1),, of lateral rise, smaller than angle 4), the incidence a, (FIG. 6) of the normal section C-C of the central portion are smaller than incidences oz (FIG. 7) of the normal sections D-D of the side portions 3b at a depth of submergence I-I greater than half chord 0" (FIG. 8).

Disposed to the aft of fore hydrofoil 3, at height K (FIG. 8) above side portions 3b thereof, this height K not exceeding endmost chord 0 (FIG. 5) of these side portions, is stabilizer 8 shaped as a foil of which span L is either greater than or equal to width M of hull l of the watercraft at the area where stabilizer 8 is mounted.

The stabilizer 8 may be composed from two portions (FIG. 9) arranged symmetrically in respect of diametral or central plane 7 of the watercraft. In this case spacing N" between the innermost ends of these portions 8a, facing diametral plane 7 of the watercraft, is smaller than width M of the hull l of the watercraft at the area adjacent to stabilizer 8.

Disposed intermediate of fore and aft hydrofoils 3 and 4, to the aft of the gravity centre 5 of the watercraft and above water line 6 corresponding to the cruising speed is middle hydrofoil 9 (FIG. 10) having relatively small angle d), of lateral rise, preferably, below 15, span P of this middle hydrofoil 9 being greater than width R of hull 1 of the watercraft at the bilge thereof, at the area where the hydrofoil 9 is mounted.

Pivotally mounted on the central portion 3a of the fore hydrofoil 3, symmetrically in respect of diametral plane 7 of the watercraft, is flap 10 (FIG. 1); similar flaps 11 (FIG. 1) are mounted on the sidemost portions of aft hydrofoil 4.

As the abovedescribed hydrofoil watercraft travels at a cruising speed, fore hydrofoil 3 thereof deforms the free surface of water, producing a wave at the rising incline of which aft hydrofoil 4 operates. Fore hydrofoil 3 featuring, in accordance with the present invention, diminishing angles (1), 4: and (p of dead rise or lateral rise of side portions 3b thereof in the direction toward the free surface of water and the suggested ratio of incidences 0: and a, there is ensured more uniform profile 12 (FIG. 3) of the cross-section of the trough of the wave at the area of the aft hydrofoil 4, as well as more uniform distribution of angles a of the positive incline of the water stream along the span of hydrofoil 4. This results in increased efficiency of the interaction of fore and aft hydrofoils 3 and 4 in the tandem system and provides for improved hydrodynamic properties of the watercraft travelling at a cruising speed.

Besides, with fore hydrofoil 3 being constructedin the above described manner, it becomes possible for the submergence of central portion 3a of the fore hydrofoil to be considerable, on account of the dead rise or lateral rise of the bottommost ends of side portions 3b of hydrofoil 3, while the abovespecified diminishing of the angle (1) of lateral rise of side portions 3b brings about a decrease in the forces of drift, when the watercraft travels under the conditions of skew roughness, and an increase in arm d of stabilizing forces 13 (FIG. 8) relative to the gravity centre 5, when the watercraft rolls; whereby there is provided better roll stability of the watercraft at a cruising speed, and that with the increased clearance and the reduced span of fore hydrofoil 3.

When taken together, all these features furnish improved seaworthiness and operating properties of the hydrofoil watercraft.

As the watercraft is rising to travel on the hydrofoils, stabilizer 8 increases the dynamic lift and thus helps the bow part of the hull to clear the water at low speeds. At

the same time, stabilizer 8 provides the reserve of board stability of the watercraft during transitory periods of its travel, when the bow part of hull 1 is clearing the water, while side portions 3b of hydrofoil 3, spaced from hull 1 to increase the seaworthiness of the watercraft, are still submerged, e.g., when the water line occupies the position shown by line 14 in FIG. 1 1.

Middle hydrofoil 9, which makes an effective use of the incline of the stream produced by fore hydrofoil 3 during transitory periods and which has a relatively small angle d), of dead rise or lateral rise, provides, while having high hydrodynamic properties, an increase of the total dynamic lift and the reduction of the degree of splashing of the stern part of the hull, on account of the deformation of the stream of water directed onto the stern part, e.g. when the water line occupies the position illustrated by line 15 in FIG. 11. Consequently, the resistance encountered by the watercraft, when it is lifting to travel on the hydrofoils, is reduced, and the starting properties thereof are improved.

Pivotal flaps l0 and 11, controlled by an automatic stabilization system (not shown in the appended drawings), are meant to compensate at least partly for the action of disturbance forces appearing when the watercraft travels on rough seas, in which way the level of overloads can be reduced and the conditions of the passengers and the crew of the watercraft, when the latter travels on rough seas, can be improved, which brings about increased seaworthiness. The efficiency of the performance of pivotal flaps l0 and 11 is provided for by their appropriate positioning and the structural features of hydrofoils 3 and 4, which have been described hereinabove.

Instead of the pivotal flaps, the herein disclosed hydrofoil watercraft can make use of any other known means adapted to adjust the lift of hydrofoils '3 and 4, e.g. means effecting aerotion of the surfaces of the hydrofoils.

What is claimed is:

l. A hydrofoil watercraft, comprising: a hull, a fore carrier hydrofoil and an aft carrier hydrofoil attached to the bottom portion of said hull, respectively, to the fore and to the aft from the gravity center of said watercraft, whereby said fore and aft hydrofoils make up a tandem" watercraft-supporting system; said fore carrier hydrofoil including a central portion and two side portions merging with said central portion, the respective upper ends of said side portions being located above the water line of said watercraft at a cruising speed thereof, each one of said side portions of said fore hydrofoil having its angles of lateral rise diminishing in the direction from the diametral central plane of said watercraft toward the respective sides thereof, such diminishing starting from the depth of submergence of said side portions in respect of said cruising speed water line, which is not smaller than half of the chord of said fore hydrofoil in place of its intersection thereof with the surface of water at said cruising speed; said central portion of said fore hydrofoil being located at a depth of submergence in respect of said cruising speed water line, which is in excess of half of the chord of said fore hydrofoil; said central portion of said fore hydrofoil having the angles of dead rise or lateral rise thereof not exceeding the respective angles of dead rise or lateral rise of said side portions of said fore hydrofoil at the points where said side portions merge with said central portion.

2. A hydrofoil watercraft according to claim 1,

wherein said angles of dead rise or lateral rise of said central portion of said fore hydrofoil are smaller than the angles of dead rise or lateral rise of said side portions of said fore hydrofoil at the points where said side portions merge with said central portion, the incidence angles of the normal sections of said central portion being smaller than the respective incidence angles of the normal sections of said side portions at the areas of said side portions which are located at a depth of submergence greater than half a chord of said fore hydrofoil, measured at the point where said fore hydrofoil intersects the surface of water at a cruising speed of said watercraft.

3. A hydrofoil watercraft according to claim 2, comprising a stabilizer mounted above said fore hydrofoil, said stabilizer including a foil having the span thereof not smaller than the width of said hull of said watercraft at the area thereof, where said stabilizer is positioned.

4. A hydrofoil watercraft according to claim 3, wherein the height of said stabilizer above said fore hydrofoil is not greater than the chord of said side portions of said fore hydrofoil, measured at the upper extremities of said side portions.

5. A hydrofoil watercraft according to claim 4, wherein said stabilizer is of a split structure, the spacing between the ends of the two portions thereof, facing the diametral central plane of said watercraft, not exceeding the width of said hull of said watercraft at the area where said stabilizer is mounted thereon.

6. A hydrofoil watercraft according to claim comprising a middle hydrofoil disposed intermediate of said fore hydrofoil and said aft hydrofoil, to the aft from said gravity center of said watercraft and above said cruising speed water line thereof, said middle hydrofoil having a relatively small angle of dead rise or lateral 

1. A hydrofoil watercraft, comprising: a hull, a fore carrier hydrofoil and an aft carrier hydrofoil attached to the bottom portion of said hull, respectively, to the fore and to the aft from the gravity center of said watercraft, whereby said fore and aft hydrofoils make up a ''''tandem'''' watercraft-supporting system; said fore carrier hydrofoil including a central portion and two side portions merging with said central portion, the respective upper ends of said side portions being located above the water line of said watercraft at a cruising speed thereof, each one of said side portions of said fore hydrofoil having its angles of lateral rise diminishing in the direction from the diametral central plane of said watercraft toward the respective sides thereof, such diminishing starting from the depth of submergence of said side portions in respect of said cruising speed water line, which is not smaller than half of the chord of said fore hydrofoil in place of its intersection thereof with the surface of water at said cruising speed; said central portion of said fore hydrofoil being located at a depth of submergence in respect of said cruising speed water line, which is in excess of half of the chord of said fore hydrofoil; said central portion of said fore hydrofoil having the angles of dead rise or lateral rise thereof not exceeding the respective angles of dead rise or lateral rise of said side portions of said fore hydrofoil at the points where said side portions merge with said central portion.
 2. A hydrofoil watercraft according to claim 1, wherein said angles of dead rise or lateral rise of said central portion of said fore hydrofoil are smaller than the angles of dead rise or lateral rise of said side portions of said fore hydrofoil at the points where said side portions merge with said central portion, the incidence angles of the normal sections of said central portion being smaller than the respective incidence angles of the normal sections of said side portions at the areas of said side portions which are located at a depth of submergence greater than half a chord of said fore hydrofoil, measured at the point where said fore hydrofoil intersects the surface of water at a cruising speed of said watercraft.
 3. A hydrofoil watercraft according to claim 2, comprising a stabilizer mounted above said fore hydrofoil, said stabilizer including a foil having the span thereof not smaller than the width of said hull of said watercraft at the area thereof, where said stabilizer is positioned.
 4. A hydrofoil watercraft according to claim 3, wherein the height of said stabilizer above said fore hydrofoil is not greater than the chord of said side portions of said fore hydrofoil, measured at the upper extremities of said side portions.
 5. A hydrofoil watercraft according to claim 4, wherein said stabilizer is of a split structure, the spacing between the ends of the two portions thereof, facing the diametral central plane of said watercraft, not exceeding the width of said hull of said watercraft at the area where said stabilizer is mounted thereon.
 6. A hydrofoil watercraft according to claim 5 comprising a middle hydrofoil disposed intermediate of said fore hydrofoil and said aft hydrofoil, to the aft from said gravity center of said watercraft and above said cruising speed water line thereof, said middle hydrofoil having a relatively small angle of dead rise or lateral rise, the span of said middle hydrofoil being not smaller than the width of said hull of said watercraft at the bilge thereof, at the area where said middle hydrofoil is mounted thereon.
 7. A hydrofoil watercraft according to claim 6, comprising a plurality of flaps pivotally mounted on said central portion of said fore hydrofoil and on the opposite side end portions of said aft hydrofoil, respectively, symmetrically in respect of said diametral central plane of said watercraft, said flaps assisting in stabilization of the travel of said watercraft on rough seas. 